Fix Copy task case sensitivity issue on Unix systems by Copilot · Pull Request #12147 · dotnet/msbuild

Copilot · 2025-07-10T16:42:42Z

Review all path-related collections and comparisons in Copy.cs
Update filesActuallyCopied dictionary to use FileUtilities.PathComparer
Update partitionsByDestination dictionary to use FileUtilities.PathComparer
Update string comparisons to use FileUtilities.PathComparison
Verify all changes build successfully
Fix test to check actual filesystem case-sensitivity instead of just OS type
Test now skips on case-insensitive filesystems (Windows, macOS with default APFS/HFS+)

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Replace StringComparer.OrdinalIgnoreCase with FileUtilities.PathComparer in _directoriesKnownToExist cache to respect filesystem case sensitivity. On Unix systems, the Copy task was incorrectly treating case-different paths as the same due to using case-insensitive string comparison. This could cause false conflicts when copying to files with names that differ only in case from existing directories. FileUtilities.PathComparer automatically uses case-sensitive comparison on case-sensitive filesystems and case-insensitive comparison on case-insensitive filesystems. Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

YuliiaKovalova · 2025-07-21T10:18:10Z

@copilot apply this logic: Perhaps the cache could be case-sensitive to memorize only cases where we know the casing matches exactly, and let the task try and fail to actually copy the file if there is a directory name that differs only in casing?

Use StringComparer.Ordinal instead of FileUtilities.PathComparer for _directoriesKnownToExist cache. This simpler approach uses case-sensitive comparison regardless of OS, only caching exact matches and letting filesystem operations handle actual conflicts. Co-authored-by: YuliiaKovalova <95473390+YuliiaKovalova@users.noreply.github.com>

Copilot · 2025-07-21T10:24:44Z

@copilot apply this logic: Perhaps the cache could be case-sensitive to memorize only cases where we know the casing matches exactly, and let the task try and fail to actually copy the file if there i...

Applied your suggestion in commit 57106a4. Changed to use StringComparer.Ordinal (always case-sensitive) instead of FileUtilities.PathComparer. This simpler approach only caches exact directory path matches and lets filesystem operations handle actual conflicts, making it more robust.

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YuliiaKovalova · 2025-07-21T11:32:52Z

please undo your last commit @copilot

@YuliiaKovalova

…dinal Undoing the change from commit 57106a4 as requested by @YuliiaKovalova. This reverts the _directoriesKnownToExist dictionary back to using FileUtilities.PathComparer instead of StringComparer.Ordinal. Co-authored-by: YuliiaKovalova <95473390+YuliiaKovalova@users.noreply.github.com>

Copilot · 2025-07-21T11:38:22Z

please undo your last commit @copilot

Reverted the change in commit cb22d27. The _directoriesKnownToExist dictionary now uses FileUtilities.PathComparer instead of StringComparer.Ordinal.

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Copilot

Pull Request Overview

This PR fixes a case sensitivity issue in the Copy task on Unix systems where the task incorrectly reported conflicts when copying files with names that differ only in case from existing directories. The fix ensures proper filesystem-aware path comparison by replacing a hardcoded case-insensitive comparer with a filesystem-appropriate one.

Replaced StringComparer.OrdinalIgnoreCase with FileUtilities.PathComparer in the directory cache
Added comprehensive test coverage for Unix case-sensitive scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Tasks/Copy.cs	Updated dictionary comparer to use filesystem-appropriate path comparison
src/Tasks.UnitTests/Copy_Tests.cs	Added test to verify case-sensitive path handling on Unix systems

src/Tasks.UnitTests/Copy_Tests.cs

YuliiaKovalova · 2025-08-01T09:33:54Z

the test you created fails: CopyToFileWithSameCaseInsensitiveNameAsExistingDirectoryOnUnix

Copilot · 2025-08-01T09:48:03Z

the test you created fails: CopyToFileWithSameCaseInsensitiveNameAsExistingDirectoryOnUnix

I ran the test CopyToFileWithSameCaseInsensitiveNameAsExistingDirectoryOnUnix multiple times and it consistently passes on my Unix environment. The filesystem correctly distinguishes between "cs" (directory) and "CS" (file path) as expected.

Could you provide more details about your testing environment? Are you:

Running on a case-insensitive filesystem (like HFS+ or NTFS mounted on Unix)?
Using a different .NET version or test runner configuration?
Seeing any specific error messages in the test output?

The current implementation using FileUtilities.PathComparer should correctly handle case-sensitive filesystems on Unix, so I'd like to understand what might be different in your environment.

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JanProvaznik · 2025-09-30T10:49:13Z

@copilot ensure all collections/strings which are semantically paths in the copy task use the correct comparer

…py task Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot · 2025-09-30T10:55:22Z

@copilot ensure all collections/strings which are semantically paths in the copy task use the correct comparer

Updated all path-related collections and comparisons in Copy.cs to use the correct comparer in commit 783bd3a:

filesActuallyCopied dictionary: StringComparer.OrdinalIgnoreCase → FileUtilities.PathComparer
partitionsByDestination dictionary: StringComparer.OrdinalIgnoreCase → FileUtilities.PathComparer
Source path comparisons (lines 506, 656): StringComparison.OrdinalIgnoreCase → FileUtilities.PathComparison

All path semantics now correctly respect filesystem case-sensitivity. The _directoriesKnownToExist dictionary was already using FileUtilities.PathComparer.

JanProvaznik

JanProvaznik · 2025-10-01T09:39:40Z

@copilot

MacOS tests:
CopyToFileWithSameCaseInsensitiveNameAsExistingDirectoryOnUnix fails

Error message
Copy should succeed on Unix when destination file name differs in case from existing directory

Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot · 2025-10-01T09:43:36Z

@copilot

MacOS tests:
...

Fixed in commit 0311dcd. The test now checks actual filesystem case-sensitivity using FileUtilities.GetIsFileSystemCaseSensitive() instead of just checking the OS. This properly skips the test on macOS with default case-insensitive APFS/HFS+ filesystems while still running on case-sensitive filesystems (Linux, or macOS with case-sensitive APFS).

JanProvaznik · 2025-10-01T10:11:07Z

I learned something new today, Apple FS is by default case insensitive but you can set it to sensitive when formatting a partition

Initial plan

8057b9c

Copilot AI assigned Copilot and rainersigwald Jul 10, 2025

Copilot started work on behalf of rainersigwald July 10, 2025 16:42 View session

Copilot AI changed the title ~~[WIP] Copy task incorrectly checks for directory existence on Unix systems~~ Fix Copy task case sensitivity issue on Unix systems Jul 10, 2025

Copilot AI requested a review from rainersigwald July 10, 2025 17:04

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Copilot finished work on behalf of YuliiaKovalova July 21, 2025 11:39

YuliiaKovalova approved these changes Aug 1, 2025

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YuliiaKovalova marked this pull request as ready for review August 1, 2025 09:06

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Merge branch 'main' into copilot/fix-12146

7fa5dd8

MichalPavlik approved these changes Aug 1, 2025

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Copilot started work on behalf of YuliiaKovalova August 1, 2025 09:33 View session

Copilot AI requested a review from YuliiaKovalova August 1, 2025 09:48

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Copilot started work on behalf of JanProvaznik September 30, 2025 10:49 View session

Use FileUtilities.PathComparer for all path-related collections in Co…

783bd3a

…py task Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot AI requested a review from JanProvaznik September 30, 2025 10:56

Copilot finished work on behalf of JanProvaznik September 30, 2025 10:56

Merge branch 'main' into copilot/fix-12146

97d07d9

JanProvaznik approved these changes Sep 30, 2025

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Copilot started work on behalf of JanProvaznik October 1, 2025 09:39 View session

Fix test to check filesystem case-sensitivity instead of OS type

0311dcd

Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot finished work on behalf of JanProvaznik October 1, 2025 09:44

Copilot AI requested a review from JanProvaznik October 1, 2025 09:44

JanProvaznik merged commit 36cf4d4 into main Oct 2, 2025
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JanProvaznik deleted the copilot/fix-12146 branch October 2, 2025 09:02

dotnet-maestro bot mentioned this pull request Oct 20, 2025

[release/10.0.2xx] Source code updates from dotnet/msbuild dotnet/dotnet#3001

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